In a state where the storage spaces of domestic nuclear power plants' keeping radioactive waste are saturated, as the prearranged date of operation of a Kyung-ju low and intermediate level radioactive waste repository has been delayed for about 2 years from the end of 2009, the development on a technology of reducing an amount of the waste generated from the nuclear power plants has risen as a very interesting present issue. Since the reported cost for permanent disposal of waste generated by the operation of a nuclear power plant exceeds about 7,400,000 won per drum, it is determined that a payment for the cost for disposal of the waste may be a considerable burden on a nuclear power plant proprietor.
Table 1 shows an examination on a trend in the recent generation of waste from domestic nuclear power plants. As a result of an analysis on the waste generated from nuclear power plants from 2006 to 2008, it was found that the percentage of miscellaneous radioactive solid waste is about 83% of the whole waste, and the percentage of combustible waste is about 55.8% of the miscellaneous radioactive solid waste. Accordingly, it is required to suggest a fundamental alternative plan for reducing the percentage of the combustible waste in the miscellaneous radioactive solid waste.
TABLE 1200620072008ratioratioratiototalindexgeneration(%)generation(%)generation(%)ratio (%)waste resin3436.23175.41964.2856 (5.4)waste filter190.3130.2100.2 42 (0.2)miscellaneouscombustible308356346458.9243551.68982 (55.8)solidincombustible206337.5208435.52074446221 (38.6)total (drum)55081005878100471510016101 (100)  * Reference document: Nuclear Power Plant White Paper 2006 to 2008
It has been examined that in a case of nuclear power plants of USA and Mexico, 85% or more of the plants participate in reducing the operating expenses of a washing room and the amount of generated waste through the use of various water-soluble protective products prepared from PVA, such as working clothes, decontamination paper, overshoes, a leakage rod, or the like. According to an EPRI report, it has been reported that the reduction ratio of waste by the use of the PVA protective products is 10,000:1.
The technology for reducing the amount of combustible waste generated from a nuclear power plant may be divided into a technology for blocking generating sources and a technology for treating generated waste. In general, it can be said that a technology capable of most effectively treating combustible waste is an incineration technology. However, in view of the present domestic affairs, there is a difficulty in that the incinerating and final-disposing of the radioactive waste within the plant are not agreeable techniques according to people's feeling, and also are contradictory to the environmentally friendly operation of a nuclear power plant proprietor. Moreover, if the management is insufficient, volatile radioactive materials may be recklessly discharged to the environment, thereby causing chronic environmental pollution. Accordingly, a solution for significantly reducing the generation amount of radioactive waste is to fundamentally block the generation of combustible waste. However, in view of the inevitability of the generation of combustible waste during the operation of a nuclear power plant, it is required to prepare a fundamental solution for reducing the generation amount of waste.
From this point of view, the introduction of protective products prepared from PVA can be a solution of the problem. PVA has a physiochemical characteristic similar to cotton unlike other polymer materials. It also has an advantage in that it is dissolved in water of 100° C. This allows radioactive materials of the waste of products prepared from PVA to be easily decontaminated below MDA, and to be biochemically treated, and allows the treated waste to be finally decomposed into CO2 and H2O. Thus, it can be said that the products are very environmentally friendly products.
In a case of domestic nuclear power plants, since the first test application of the use of PVA protective products in 2007, the usage amount tends to be gradually increased. Also, the kinds of the products used in the nuclear power plants are variously changed, from working clothes at the initial stage, to decontamination paper, vinyl, overshoes, gloves, a leakage absorbing rod, or the like.
U.S. Pat. No. 7,147,787 and Korea Patent No. 2002-0063896 disclose an apparatus and a method for completely dissolving, and sterilizing clothes, supplies, devices, and other products, prepared from PVA, and removing radioactive materials from the products, which decomposes PVA into organic acid and finally treats the decomposed PVA in a foul water drain system. In the method disclosed in the patents, a PVA material is dissolved in 0.5˜5 w/v %, decomposed into organic acid by using a —OH radical, and treated by using a general domestic sewage treatment stream. The method disclosed in the patents is very advantageous in terms of volume reduction and treatment expenses of radioactive waste. However, in a case of a domestic nuclear power industry, the taking out of radioactive waste is strictly limited, and the treatment method of the waste is also limited to incineration, which in actuality does not allow the waste to be entrusted to an operator operating a biological treatment facility. Accordingly, it is immediately required to develop an efficient PVA protective product treatment technology in accordance with domestic affairs.
Issued Korean Patent No. 10-0823961 discloses a method for treating PVA protective products, in which a plasma incinerator is used to high-temperature-incinerate them. The treatment method of the patent includes technical features required to be additionally complemented in that the incineration of the PVA solution in a high-temperature condition of 1000° C. or more generates a large amount of nitrogen oxide, the use of auxiliary fuel for two-stage combustion increases operating expenses, and the combustion of a liquid containing high-concentration PVA materials in the use of a plasma generator may generate soot due to an un-burned reaction.
In order to reduce an operation cost of a nuclear power plant, and to give an environmentally friendly image to the nuclear power industry through the introduction of PVA protective products capable of significantly reducing the amount of waste generated from domestic nuclear power plants, it is desired to develop a treatment method which can sufficiently utilize environmentally friendly characteristics of PVA protective products.